Write a c program called assignment4.c, that creates a linked list of customer data. each entry in the list is to have the customer’s last name, first name, id (int), balance (float), and a pointer to the next customer data. create a struct for the customer first. then create a pointer ("head") that points to the first element in the linked list (initially null), as a global variable. also, you need to create the following functions: int insertatindex(char * lastname, char * firstna